The following script will perform javascript validation of E-mail addresses.
Comments to craig@siliconglen.com.
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<!-- TWO STEPS TO INSTALL EMAIL ADDRESS VALIDATION: 1. Copy the coding into the HEAD of your HTML document 2. Add the last code into the BODY of your HTML document --> <!-- STEP ONE: Paste this code into the HEAD of your HTML document --> <HEAD> <SCRIPT TYPE="text/javascript"> <!-- Original author: Sandeep V. Tamhankar (stamhankar@hotmail.com) --> <!-- old Source on http://www.jsmadeeasy.com/javascripts/Forms/Email%20Address%20Validation/template.htm --> <!-- The above address bounces and no current valid address --> <!-- can be found. This version has changes by Craig Cockburn --> <!-- to accommodate top level domains .museum and .name --> <!-- plus various other minor corrections and changes --> /* 1.1.3: Amended error messages and allowed script to deal with new TLDs 1.1.2: Fixed a bug where trailing . in e-mail address was passing (the bug is actually in the weak regexp engine of the browser; I simplified the regexps to make it work). 1.1.1: Removed restriction that countries must be preceded by a domain, so abc@host.uk is now legal. 1.1: Rewrote most of the function to conform more closely to RFC 822. 1.0: Original */ <!-- Begin function emailCheck (emailStr) { /* The following pattern is used to check if the entered e-mail address fits the user@domain format. It also is used to separate the username from the domain. */ var emailPat=/^(.+)@(.+)$/ /* The following string represents the pattern for matching all special characters. We don't want to allow special characters in the address. These characters include ( ) < @ , ; : \ " . [ ] */ var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]" /* The following string represents the range of characters allowed in a username or domainname. It really states which chars aren't allowed. */ var validChars="\[^\\s" + specialChars + "\]" /* The following pattern applies if the "user" is a quoted string (in which case, there are no rules about which characters are allowed and which aren't; anything goes). E.g. "jiminy cricket"@disney.com is a legal e-mail address. */ var quotedUser="(\"[^\"]*\")" /* The following pattern applies for domains that are IP addresses, rather than symbolic names. E.g. joe@[123.124.233.4] is a legal e-mail address. NOTE: The square brackets are required. */ var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/ /* The following string represents an atom (basically a series of non-special characters.) */ var atom=validChars + '+' /* The following string represents one word in the typical username. For example, in john.doe@somewhere.com, john and doe are words. Basically, a word is either an atom or quoted string. */ var word="(" + atom + "|" + quotedUser + ")" // The following pattern describes the structure of the user var userPat=new RegExp("^" + word + "(\\." + word + ")*$") /* The following pattern describes the structure of a normal symbolic domain, as opposed to ipDomainPat, shown above. */ var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$") /* Finally, let's start trying to figure out if the supplied address is valid. */ /* Begin with the coarse pattern to simply break up user@domain into different pieces that are easy to analyze. */ var matchArray=emailStr.match(emailPat) if (matchArray==null) { /* Too many/few @'s or something; basically, this address doesn't even fit the general mould of a valid e-mail address. */ alert("Email address seems incorrect (check @ and .'s)") return false } var user=matchArray[1] var domain=matchArray[2] // See if "user" is valid if (user.match(userPat)==null) { // user is not valid alert("The part of your email address before the '@' doesn't seem to be valid.") return false } /* if the e-mail address is at an IP address (as opposed to a symbolic host name) make sure the IP address is valid. */ var IPArray=domain.match(ipDomainPat) if (IPArray!=null) { // this is an IP address for (var i=1;i<=4;i++) { if (IPArray[i]>255) { alert("Destination IP address is invalid!") return false } } return true } // Domain is symbolic name var domainArray=domain.match(domainPat) if (domainArray==null) { alert("Part of your email address after the '@' doesn't seem to be valid") return false } /* domain name seems valid, but now make sure that it ends in a three-letter word (like com, edu, gov) or a two-letter word, representing country (uk, nl), and that there's a hostname preceding the domain or country. */ /* Now we need to break up the domain to get a count of how many atoms it consists of. */ var atomPat=new RegExp(atom,"g") var domArr=domain.match(atomPat) var len=domArr.length if (domArr[domArr.length-1].length<2 || domArr[domArr.length-1].length>6) { // the address must end in a two letter or other TLD including museum alert("The address must end in a top level domain (e.g. .com), or two letter country.") return false } // Make sure there's a host name preceding the domain. if (len<2) { var errStr="This address is missing a hostname!" alert(errStr) return false } // If we've got this far, everything's valid! return true; } // End --> </script> </head> <!-- STEP TWO: Copy this code into the BODY of your HTML document --> <BODY> <center> <form name=emailform onSubmit="return emailCheck(this.email.value);"> Your Email Address: <input type=text name="email"><br> <input type=submit value="Submit"> </form> </center>